Visual effects have the potential to expand the viewing enjoyment of moviegoers. For example the movement effect ‘Bullet Time’ utilized in the movie ‘The Matrix’ was critical to the appeal of the movie.
Visual effects for 3-dimensional motion pictures have been used commercially since the early 1950s, and include such motion pictures as ‘Charge at Feather River’, starring Guy Madison. The ‘Vincent Price movie ‘House of Wax’ was originally released as a 3-D thriller. The 3-D movie fad of the early to mid-1950s however soon faded due to complexity of the technologies and potential for improper synchronization, and alignment of left and right eye images as delivered to the viewer.
“Visual effects for 3-dimensional motion pictures have been used commercially since the early 1920s, and include such motion pictures as ‘Charge at Feather River’, starring Guy Madison. The ‘Vincent Price movie ‘House of Wax’was originally released as a 3-D thriller. The 3-D movie fad of the early to mid-1950s however soon faded due to complexity of the technologies and potential for improper synchronization, and alignment of left and right eye images as delivered to the viewer.”
With the exception of Sony I-max 3-D presentations, which require special theater/screening facilities unique to the requirements of I-Max technology, 3-dimensional motion pictures remain a novelty. Despite the wide appeal to viewers, the difficulties and burden on motion picture producers, distributors, motion picture theaters, and on the viewers has been a barrier to their wide scale acceptance.
1. Vision
The Human Eye And Depth Perception
The human eye can sense and interpret electromagnetic radiation in the wavelengths of about 400 to 700 nanometers—visual light to the human eye. Many electronic instruments, such as camcorders, cell phone cameras, etc., are also able to sense and record electromagnetic radiation in the band of wavelengths 400-700 nanometer.
To facilitate vision, the human eye does considerable ‘image processing’ before the brain gets the image. As examples:
When light ceases to stimulate the eyes photoreceptors, the photoreceptors continue to send signals, or ‘fire’ for a fraction of a second afterwards. This is called ‘persistence of vision’, and is key to the invention of motion pictures that allows humans to perceive rapidly changing and flickering individual images as a continuous moving image.
The photoreceptors of the human eye do not ‘fire’ instantaneously. Low light conditions can take a few thousands of a second longer to transmit signals than under higher light conditions. Causing less light to be received in one eye than another eye, thus causing the photoreceptors of the right and left eyes to transmit their ‘pictures’ at slightly different times, explains in part the Pulfrich 3-D illusion, which is utilized in the invention of a Pulfrich Filter Spectacles.
Once signals are sent to the eye, the brain process the dual stereo images together (images received from the left and right eye) presenting the world to the human eye in 3-dimensions or with ‘Depth Perception’. This is accomplished by several means that have been long understood.
Stereopsis is the primary means of depth perception and normally requires sight from both eyes. The brain processes the dual images, and triangulates the two images received from the left and right eye, sensing how far inward the eyes are pointing to focus the object.
Perspective uses information that if two objects are the same size, but one object is closer to the viewer than the other object, then the closer object will appear larger. The brain processes this information to provide clues that are interpreted as perceived depth.
Motion parallax is the effect that the further objects are away from us, the slower they move across our field of vision. The brain processes motion parallax information to provide clues that are interpreted as perceived depth.
Shadows provide another clue to the human brain, which can be perceived as depth. Shading objects, to create the illusions of shadows and thus depth, is widely used as in the shading of text to produce a 3-dimensional impression without actually penetrating (perceptually) the 2-D screen surface.
2. 3-D Motion Pictures
Methods of Producing 3-D Illusion in Moving Pictures
Motion pictures are images in 2-dimensions. However, several methods have been developed for providing the illusion of depth in motion pictures. These include the Pulfrich, and Analglyph 3-dimensional illusions.
Analglyph 3-Dimensional Illusion
“Analglyph” refers to the red/blue or red/green glasses that are used in comic books and in cereal packets etc. The glasses consist of nothing more than one piece of transparent blue plastic and one piece of transparent red plastic. These glasses are easy to manufacture and have been around since the 1950s.
An analglyph stereo picture starts as a normal stereo pair of images, two images of the same scene, shot from slightly different positions. One image is then made all green/blue and the other is made all red, the two are then added to each other.
When the image is viewed through the glasses the red parts are seen by one eye and the other sees the green/blue parts. This effect is fairly simple to do with photography, and extremely easy to do on a PC, and it can even be hand-drawn. The main limitation of this technique is that because the color is used in this way, the true color content of the image is usually lost and the resulting images are in black and white. A few images can retain their original color content, but the photographer has to be very selective with color and picture content.
Pulfrich 3-Dimensional Illusion
Pulfrich was a physicist that recognized that images that travel through a dark lens take longer to register with the brain than it does for an image that passes through a clear lens. The delay is not great—just milliseconds—just enough for a frame of video to arrive one frame later on the eye that is covered by a darker lens than a clear lens. Pulfrich spectacles then have one clear lens (or is absent a lens) that does not cause a delay, and one darkened lens that slightly delays the image that arrives to the eye. In a motion picture viewed through Pulfrich lenses, for an object moving laterally across the screen, one eye sees the current frame and the other eye a previous frame.
The disparity between the two images is perceived as depth information. The brain assumes both frames belong to the same object and the viewer's eyes focus on the object as if it were closer than it is. The faster the object moves, the more separation there is between the time-delayed images, and the closer the object appears. The fact that faster objects appear closer than slower objects also coincides with the principles of motion parallax. Generally, however, the greater displacements frame to frame (and now eye to eye) result from degrees of closeness to the recording camera (proximity magnifies), so that Pulfrich viewing can deliver an approximately correct and familiar depth likeness. While the depth likeness is unquestionably 3-D, it may differ from the fixed constant of an individual's inter-ocular distance when observing the world directly. Few observers will notice this anymore than they are bothered by the spatial changes resulting from use of telephoto or wide-angle lens in filming scenes.
Motion pictures made for the Pulfrich method can be viewed without any special glasses—appearing as regular motion pictures minus the 3-D effect. Also, motion pictures made without regard for the Pulfrich effect, will still show the 3-D visual effect if lenses are worn and appropriately configured.
The limitation of the Pulfrich technique is that the 3-dimensional illusion only works for objects moving laterally or horizontally across the screen. Motion pictures made to take advantage of these glasses contain lots of horizontal tracking shots or rotational panning shots to create the effect. Pulfrich, who first described this illusion, was blind in one eye, and was never able to view the illusion, though he completely predicted and described it.
A basic example of the Pulfrich illusion can be seen by viewing either of two TV stations. The news headlines on the CNN Television network or the stock market quotations on CNBC scroll in from the right of the TV screen and across and off the screen to the left. The news or quotations appear in a small band across the bottom of the screen while the network show appears above the scrolling information. When either of these network stations is viewed through Pulfrich glasses, with the darkened lens covering the left eye and the clear lens covering the right eye, the scrolling information appears in vivid 3-dimensions appearing to be in front of the TV screen. If the lenses are reversed with the clear lens covering the left eye and the darkened lens covering the right eye, the scrolling information appears to the viewer as receded, and behind the TV screen.
Another example of the Pulfrich illusion can be seen in the movie ‘The Terminator’, starring Arnold Schwarzenegger. Any off-the-shelf copy of the movie—VCR tape, or DVD, can be viewed on a TV or PC playback display monitor as originally intended by the filmmaker. But, viewing scenes that include lateral motion from ‘The Terminator’, such as the scene when Sarah Connors enters a bar to call police (about 29 minutes into the movie) when viewed through Pulfrich glasses (left eye clear lens and right eye dark lens) shows the scene vividly in 3-dimensions, even though this visual effect was totally unintended by the director and cinematographer.
Another stunning example is the famous railroad yard scene from “Gone with the Wind”, in which Scarlett O'Hara played by Vivien Leigh walks across the screen from the right as the camera slowly pulls back to show the uncountable wounded and dying confederate soldiers. When viewed through Pulfrich glasses with (left eye clear lens and right eye dark lens), the scene appears to the user in 3-dimensions, even thought it was totally unintended by the director and cinematographer. Interesting here is that the main movement of this scene was created by the camera lifting and receding and so expanding the view. Effective lateral motion resulting from such camera movement would in fact be to only one side of the screen, which the viewers will utilize to interpret the entire scene as in depth.
The Pulfrich Filter Spectacles will allow any movie, such as “Gone with the Wind” which was shot in 1939, to be viewed in 3-dimensions. In the preferred embodiment, all that is necessary is post-production be performed on the motion picture, to identify synchronization events, and add (mix) to the soundtrack of the motion picture the sounds above human hearing that signal control of the Pulfrich Filter Spectacles, and that allow the film to be viewed with a 3-dimensional effect. Absent the Pulfrich Filter Spectacles, the viewer sees and hears the motion picture ‘Gone with the Wind’ as originally filmed.
Note that the Pulfrich 3-D effect will operate when the left or right filtering does not correspond with the direction of an image's movement on the screen. The depth-impression created is unnatural, a confusion of solid and open space, of forward and rear elements. When confronted by such anomalous depth scenes, most minds will ‘turn off’, and not acknowledge the confusion. For normal appearing 3-D, mismatched image darkening as related to the direction of the image's movement on the screen must be avoided.
We have described the need to match horizontal direction of foreground screen-movement to Left or Right light-absorbing lens. This, however, is a rule that often has to be judiciously extended and even bent, because all screen-action appropriate to Pulfrich 3-D is not strictly horizontal; horizontal movements that angle up or down, that have a large or even dominant element of the vertical, may still be seen in depth. Even a single moving element in an otherwise static scene can be lifted into relief by way of an adroit application of a corresponding Pulfrich filter. There would even be times when a practiced operator would choose to schedule instances of lens-darkening contrary to the matching-with-foreground-direction rule; the explanation for this lies in the fact that the choice of left or right filter-darkening will pull forward any object or plane of action moving in a matching direction, and there are times when the most interesting action in a picture for seeing in 3D could be at some distance from the foreground, even requiring a Left/Right filter-match at odds with the filter-side that foreground-movement calls for. For instance, if one wished to see marchers in a parade marching Left, to lift them forward of their background would require darkening of the Left lens, but foreground movement could be calling for a Right lens darkening; this would be a situation when a choice might be made to over-ride the foreground-matching rule. In most instances the rule is to be followed, but not mechanically; screen movement is often compound and complex, and an observant individual could arrange a Pulfrich timing for a movie with an alertness to such subtleties that did not limit decisions to recognition of foreground direction alone. As mentioned earlier, there would even be times, when the recording camera had moved either forward or backwards through space, when both Left and Right lenses would half-darken to either side of their centers, outer halves darkening moving forward (with picture elements moving out to both sides from picture-center) or both inner halves darkening when retreating backwards (with picture elements moving in towards center from each side).
One might think that alternating between the screenflatness of a dialogue scene and the deep space of an action scene would disrupt the following of a story. In fact, just as accompanying movie-music can be intermittent while entirely supporting a story development, dialogue is best attended to with the screen flat and action-spectacle is most effective given the dimension and enbanced clarity of depth. Usually a function of lighting specialists, it is at ays necessary to make objects and spaces on a flat screen appear distinct from each other; besides making a scene move convincing, 3-D separation of forms and of spatial volumes one from the other speeds up the “reading” of what are essentially spatial events. This is to say: flat can best enable concentration on dialogue; depth-dimension can most effectively deliver action scenes. Alternating between 2-D and 3-D awareness is something we even do, to a degree, in our experience of actuality, as a function of our changing concentration of attention; just as we hear things differently when we concentrate on listening Then, too, making sense of movies is a thing we learn to do, as different from life-experience as a movie is with its sudden close-ups and change of angle and of scene, its flashbacks, et cetera. Movie viewing is a learned language, a form of thinking; the alternating of flat-screen information with depth-information will be as readily adapted to as many other real-world-impossibility accepted without question as natural to the screen.
In the preferred embodiment of the Pulfrich Filter Spectacles invention—we focus on a better means to present the Pulfrich 3-D illusion in motion pictures by precisely signaling the synchronization of the Pulfrich Filter Spectacles lenses to the motion picture. In other embodiments of the invention, similar principles can be utilized to present other illusions or special effects in motion pictures.
Problems with 3-D Motion Pictures
With the exception of Sony I-Max 3-d, a special cine-technology requiring theaters exclusively designed for its screening requirements, 3-dimensional motion pictures have never caught on except as a short-term fad, because a myriad of problems continue to make 3-dimensional motion pictures unacceptable to producers and viewers of motion pictures. Despite concerted efforts, 3-dimensional motion pictures continue to be nothing more than a novelty. There are many problems and constraints involving the production, projection, and viewing of 3-dimensional motion pictures.
Production: The commonly used analglyph 3-dimensional movie systems require special cameras that have dual lenses, and capture 2-images on each frame. To have a version of the motion picture that can be viewed without special glasses requires that a separate version of the motion picture be shot with a regular camera so there is only one image per video frame or special re-photography and re-printing of the 3-D motion picture is required.
Projection: Some 3-dimensional systems require the synchronization and projection by at least 2 cameras in order to achieve the effect. “Hitachi, Ltd has developed a 3D display called Transpost 3D which can be viewed from any direction without wearing special glasses, and utilize twelve cameras and rotating display that allow Transpost 3D motion pictures that can be seen to appear as floating in the display. The principle of the device is that 2D images of an object taken from 24 different directions are projected to a special rotating screen. On a large scale this is commercially unfeasible, as special effects in a motion picture must be able to be projected with standard projection equipment in a movie theater, TV or other broadcast equipment.
Viewing: As a commercial requirement, any special effect in a motion picture must allow viewing on a movie screen, and other viewing venues such as TV, DVD, VCR, PC computer screen, plasma and LCD displays. From the viewers vantage, 3-dimensional glasses, whether analglyph or Pulfrich glasses, which are used in the majority of 3-dimensional efforts, if poorly made or worn incorrectly are uncomfortable and may cause undue eye strain or headaches. Experiencing such headache motivates people to shy away from 3-D motion pictures.
Polaroid projection requires a metallic-surface screen. Should the two film-strands used in a double-projection screening lose synchronization or precise screen alignment, the effect is sure to cause great discomfort, as well as loss of the 3D illusion.
Because of these and other problems, 3-dimensional motion pictures have never been more than a novelty. The inconvenience and cost factors for producers, special equipment projection requirements, and viewer discomfort raise a sufficiently high barrier to 3-dimensional motion pictures that they are rarely produced. A main object of this invention is to overcome these problems and constraints.
Attempts to Overcome the Problems of 3-D Motion Pictures
Different formulations of shutter glasses have been implemented over the last few decades, but without much large-scale commercial success. A shutter glasses solution generally require two images for each image of video, with shutter covering or uncovering each eye of the viewer. This allows one eye to see, than the other, with the shutters timed and synchronized with the video so that each eye only sees the image intended for it. Recent advances have eliminated mechanical shutter, and now use lens that turn opaque when an electric current is passed through it.
Some shutter glass systems are wired to a control device while some shutter glass systems use wireless infrared signaling to control the state of the lenses.
CrystalEyes is the name of a stereoscopic viewing product produced by the StereoGraphics Corporation of San Rafael, Calif. They are lightweight, wireless liquid crystal shuttering eyewear that are used to allow the user to view alternating field sequential stereo images. The source of the images alternately displays a left-eye view followed by a right-eye view. CrystalEyes' shutters can block either of the user's eyes so that only images appropriate for each eye are allowed to pass. A wireless infrared communications link synchronizes the shuttering of the eyewear to the images displayed on the monitor or other viewing screen. CrystalEyes shutter glasses, weight only 3.3 ounces, use two 3V lithium/manganese dioxide batteries, and have a battery life of 250 hours. This demonstrates the robustness and potential of a viewer glass solution.
Because shutter glasses only expose each eye to every other frame, the refresh rate of the video is effectively cut in half. On a TV with refresh rates of 30 frames per second (for an NTSC TV) or 25 frames per second (for a PAL TV), this is hard on the eyes because of the continual flicker. This problem is eliminated with higher refresh rates, such as on PC monitors.
However, shutter systems have not been overwhelmingly commercially successful. Motion pictures that use such stereo shutter systems require two frames for each frame of regular film. Motion pictures would then have to be produced in at least 2 versions. Also, except on high refresh rate systems, such as expensive PC monitors, the viewer sees too much ‘flicker’ causing distraction and annoyance. An additional requirement and burden is the wired or wireless signaling to control the state of the lens. LCD screens that are used on laptops generally do not have high enough refresh rates for stereoscopic shutter 3D systems. Shutter systems generally do not work well with LCD or movie projectors.
In the preferred embodiment of this invention, in a manner similar to that used with some versions of shutter glasses, we utilize lens materials that are clear when no current is passed through it, but partially occluded or darkened when a current above a threshold voltage is passed through it.